JP6137872B2 - Method for producing rubber composition - Google Patents

Description

  The present invention relates to a pneumatic tire, in particular, a pneumatic tire (hereinafter referred to as a run-flat tire) that can run even when the internal pressure of the tire (hereinafter referred to as internal pressure) is reduced due to puncture or the like, and a sidewall thereof. It is related with the manufacturing method of the rubber composition of a reinforced rubber member arrange | positioned in a crescent shape at a part.

In recent years, as the speed of vehicles has increased, the demand for higher performance of tires has increased further, but even if the filling pressure of the tires has decreased due to the demand for weight reduction of the vehicles due to spare tires, i.e. punctures, the load is supported. There is a demand for tires that can continue to run.
A typical example of this is a pneumatic radial tire (run flat tire) with a structure in which the inner surface of the carcass layer in the area from the vicinity of the upper end of the rim flange to the end of the belt layer is reinforced with a crescent-shaped side reinforcing rubber layer. Has been proposed and put to practical use.
The characteristics required for the side reinforcing rubber of the run-flat tire are to improve the run-flat durability and to maintain the riding comfort during normal driving. The run-flat durability depends on the thickness and properties of the side reinforcing rubber itself, and the composition for that purpose is devised.

  In the blending, an improvement is made by adding components having various roles such as inorganic fillers such as carbon black and silica, vulcanizing agents, vulcanization accelerators, and anti-aging agents. In any case, if only the component is used frequently, the specific physical property is improved, but on the other hand, other physical properties are impaired, and it is necessary to balance the component.

しかしながら、上記化合物を配合した場合、老化防止剤を増量せずに、ランフラット性能も、向上させることができる加硫促進剤として、述べられてはいるものの、その効果は限定的であり、特に、天然ゴムの含有量が増加すると、効果が小さくなり、混練方法によっては、やはり老化物性の低下が避けられないといった問題があった。 For example, Patent Document 1 discloses that a bis (2-benzothiazyl) disulfide derivative represented by the following formula is blended as a vulcanization accelerator in a sidewall reinforcing rubber.

However, when the above compound is blended, although described as a vulcanization accelerator that can improve run-flat performance without increasing the amount of anti-aging agent, its effect is limited, especially When the content of natural rubber is increased, the effect is reduced, and depending on the kneading method, there is still a problem that deterioration of aging properties cannot be avoided.

  In addition, in the rubber composition that requires vulcanization when each component is added, the components excluding components directly related to vulcanization are kneaded in the previous stage, and then in the subsequent stage. Adding a sulfur and a vulcanization accelerator is a common formulation.

JP 2010-285514 A

  It aims at improving the aging physical property at the time of using a bis (2-benzothiazyl) disulfide derivative as a vulcanization accelerator.

  As an idea of the compounding prescription of each component, when compounding is performed in multiple stages, which component is blended at which stage, etc. It can be a factor.

  Therefore, the inventor of the present application has studied the stage of blending this component, and as a result, in general, zinc white blended in the stage prior to vulcanization in kneading is a component necessary for vulcanization, sulfur and vulcanization acceleration. It has been found that, by blending simultaneously with the agent, there is an effect in preventing the deterioration of aging physical properties, and the present invention has been achieved.

〔上記式（Ｉ）中のＲ^１、Ｒ^２は水素原子、炭素数１〜４の直鎖アルキル基又はアルコキシ基、炭素数３〜４の分岐アルキル基又はアルコキシ基であり、これらは同一であっても異なっていてもよい。〕
（２）混練方法が複数段階からなり、天然ゴムをゴム成分の３０重量％以上含むゴム成分（Ａ）と、充填剤とを混練する工程と、前記工程により得られたゴム組成物に硫黄と式（Ｉ）で表される化合物とを混練する工程とを含み、硫黄と式（Ｉ）で表される化合物とを混練する工程で亜鉛華をゴム成分１００重量部に対し１〜３重量部配合することを特徴とする、（１）に記載のゴム組成物の製造方法。
（３）天然ゴムをゴム成分の６０重量％以上含むことを特徴とする（１）又は（２）記載のゴム組成物の製造方法。
（４）硫黄と式（Ｉ）で表される化合物とを混練する工程においてビスマレイミド、メタクリル酸若しくはアクリル酸の金属塩、または二次老化防止剤として、２−メルカプトベンズイミダゾール、又はその亜鉛塩であるイミダゾール系化合物を配合することを特徴とする、（２）又は（３）に記載のゴム組成物の製造方法。 That is, the present invention resides in the following (1) to (4).
(1) When a compound represented by the following formula (I) is kneaded, 1 to 3 parts by weight of zinc white is blended with 100 parts by weight of a rubber component, to produce a rubber composition Method.

[R ¹ and R ² in the above formula (I) are a hydrogen atom, a linear alkyl group having 1 to 4 carbon atoms or an alkoxy group, a branched alkyl group having 3 to 4 carbon atoms or an alkoxy group, and these are the same. It may or may not be. ]
(2) The kneading method comprises a plurality of stages, a step of kneading a rubber component (A) containing natural rubber at 30% by weight or more with a filler, and sulfur in the rubber composition obtained by the above step. A step of kneading the compound represented by formula (I) with 1 to 3 parts by weight of zinc white in 100 parts by weight of the rubber component in the step of kneading sulfur and the compound represented by formula (I) The method for producing a rubber composition according to (1), wherein the rubber composition is blended.
(3) The method for producing a rubber composition according to (1) or (2), wherein natural rubber is contained in an amount of 60% by weight or more of the rubber component.
(4) 2-mercaptobenzimidazole or a zinc salt thereof as bismaleimide, a metal salt of methacrylic acid or acrylic acid, or a secondary anti-aging agent in the step of kneading sulfur and the compound represented by formula (I) The method for producing a rubber composition according to (2) or (3), wherein an imidazole compound is added.

  ADVANTAGE OF THE INVENTION According to this invention, the rubber composition for run flat tires which was compatible with the run flat durability and aging physical property which are not in the past is obtained.

In this invention, when kneading | mixing the compound represented by following formula (I), 1-3 weight part zinc white is mix | blended with respect to 100 weight part of rubber components, It is characterized by the above-mentioned.

R ¹ and R ² in the compound represented by the general formula (I) are a hydrogen atom, a linear alkyl group having 1 to 4 carbon atoms or an alkoxy group, a branched alkyl group having 3 to 4 carbon atoms or an alkoxy group. These may be the same or different, and in the case of an alkyl group or alkoxy group having 1 to 4 carbon atoms, it is preferably 1 carbon atom, and particularly preferably a hydrogen atom. In any case, this is because the ease of synthesis of the compound and the vulcanization rate do not slow down.
Specific examples of R ¹ and R ² of the compound represented by the general formula (I) include methyl group, ethyl group, 1-propyl group, 2-propyl group, 1-butyl group, 2-butyl group, 2 -Methyl-1-propyl group, 2-methyl-2-propyl group, methoxy group, ethoxy group, 1-propoxy group, 2-propoxy group, 1-butoxy group, 2-butoxy group, 2-methyl-1-propoxy Group, 2-methyl-2-propoxy group.

  In the prescription of the rubber composition, when the components are compounded in a plurality of stages, a step of kneading the rubber component (A), a component mainly composed of a filler, other than the components accompanying vulcanization, and accompanying the vulcanization It is common to perform the process separately from the kneading step with the components added. Since the compound represented by the general formula (I) is one kind of vulcanization accelerator, it is blended in a kneading step by adding components accompanying vulcanization. By blending 1 to 3 parts by weight with respect to 100 parts by weight of the rubber component in the step of adding the compound represented by sulfur and the general formula (I) to the zinc white blended in the previous step, It is possible to prevent the deterioration of the aging physical properties derived from the kneading, which is a phenomenon in which the polymer chain of the rubber component (A) is broken by kneading.

  The rubber component (A) is at least one rubber component selected from natural rubber and synthetic diene rubber. Examples of the synthetic diene rubber include polyisoprene rubber (IR) and cis-1,4-polybutadiene rubber. (BR), styrene-butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR) and the like. The effect of the present application is seen when natural rubber is blended in an amount of 30% by weight or more of the rubber component as the rubber component, and the effect is seen more when it is 60% by weight or more.

  As the synthetic diene rubber contained in the rubber component (A), a modified diene rubber having a functional group containing an element selected from tin, nitrogen, and silicon at the polymer terminal can be used. Such a modified diene rubber can be synthesized according to a known method as disclosed in, for example, Japanese Patent Application Laid-Open No. 2002-144807, and a conjugated diene monomer is formed in an organic metal in a hydrocarbon solvent. It is obtained by polymerization by living anionic polymerization using a compound, preferably an organolithium compound as an initiator. At this time, by adding ethers which are coordinating oxygen donors, tertiary amines which are nitrogen donors, particularly those capable of multidentate coordination, such as organolithium compounds used as initiators, When the association state of the organometallic compound is changed or a secondary amine is added, it is induced by a lithium amide initiator, thereby allowing cis / trans geometric isomerism selectivity in 1,4-polymerization in the polymer chain. Alternatively, the amount of vinyl bonds generated by 1,2-polymerization can be changed. Thus, after conducting the polymerization reaction, a functional group-introducing agent containing tin, nitrogen and / or silicon is reacted with the living anionic polymerization terminal, which still has nucleophilicity, to thereby provide a functional group containing these elements. A modified diene rubber having a group can be synthesized.

  When the functional group introduced into the modified diene rubber is a functional group containing tin, a trihalostannyl group, a dihaloalkylstannyl group, a dihaloarylstannyl group, a halodialkylstannyl group, a halodiarylstannyl group , Trialkylstannyl group, triarylstannyl group, and the like, and the halogen atom on tin is a fluorine atom, a chlorine atom, or a bromine atom. In the case of a functional group containing nitrogen, an isocyanato group, amino group, primary amino group, secondary amino group, amide group, imide group, and other nitrogen-containing heterocyclic functional groups are exemplified. In the case of a functional group containing silicon, a trialkoxysilyl group, a dialkoxyalkylsilyl group, a dialkoxyarylsilyl group, an alkoxydialkylsilyl group, an alkoxydiarylsilyl group, a trialkylsilyl group, a triarylsilyl group, etc. may be mentioned. . When these functional groups have an alkyl group or an aryl group, a linear alkyl group having 1 to 8 carbon atoms, a branched alkyl group having 3 to 8 carbon atoms, a cyclic alkyl group having 5 to 8 carbon atoms, or a 6 to 14 carbon atoms. An aryl group containing an aromatic ring, which is substituted with a hydroxyl group, alkoxy group, acyl group, amino group, primary amino group, secondary amino group, nitro group, nitroso group, mercapto group, sulfo group, halogen atom, etc. May be. Moreover, when it is an alkoxy group, it has the said hydrocarbon group which is an alkyl group or an aryl group.

  By using the above-mentioned modified diene rubber, it is possible to suppress a decrease in elastic modulus due to temperature rise and improve low heat buildup in the carbon black compounded rubber composition, so that the run flat performance is maintained, Aging physical properties can also be improved.

  In the kneading step before vulcanization, in addition to the above-mentioned normal rubber component and modified diene rubber, fillers such as carbon black and / or silica which are normal additive components, silane coupling agents In addition, kneading can be performed by blending process oil and stearic acid. Carbon black can be blended in an amount of 30 to 100 parts by weight, preferably 50 to 80 parts by weight, based on 100 parts by weight of the rubber component. When silica is blended simultaneously, it is preferable to blend 50 to 150 parts by weight in total of carbon black and silica.

  In the above process, sulfur, a vulcanization accelerator, an anti-aging agent and the like are further added to the composition kneaded in the above process, and the following kneading process is performed. Here, as a feature of the present invention, a vulcanization accelerator to be added is added. As one of the above, together with the compound represented by the general formula (I), by adding zinc white at a weight ratio of 1 to 3 parts by weight with respect to 100 parts by weight of the rubber component, kneading It is possible to prevent the cleaving of the polymer chain from being broken, and to improve the aging physical properties so as not to deteriorate.

  As an amount of zinc white sufficient to allow the compound represented by the general formula (I) and a vulcanization accelerator including the other to act efficiently, 1 part by weight or less with respect to 100 parts by weight of the rubber component, Vulcanization takes a long time and the productivity is deteriorated. When the amount exceeds 3 parts by weight, excessively mixed zinc white remains as particles in the rubber composition, which is a cause of deterioration of mechanical properties. Absent. This tendency is more prominent as the proportion of natural rubber in the rubber component increases.

  In addition to the compound represented by the general formula (I), the vulcanization accelerator is a compound selected from 2-benzothiazylsulfenamides, thiuram disulfides, thiazoles, guanidines, dithiocarbamates, and the like. One or more may be used in combination. These vulcanization accelerators can be used together in an amount of 1 to 10 parts by weight, preferably 2 to 8 parts by weight, particularly preferably 3 to 6 parts by weight, based on 100 parts by weight of the rubber component.

  In the kneading step in which sulfur and the compound represented by the general formula (I) are blended, in addition to this, bismaleimide, zinc salt of acrylic acid or methacrylic acid, or 2-mercaptobenzimidazole or its secondary as a secondary anti-aging agent An imidazole compound that is a zinc salt can be blended. When mix | blending these, 0.1-10 weight part can be mix | blended with respect to 100 weight part of rubber components, 0.3-5 weight part is preferable and 0.5-3 weight part is especially preferable. By blending these compounding agents or secondary anti-aging agents, radicals generated during kneading or deterioration during vulcanization / use can be trapped to improve aging properties.

  In the invention of the present application, aging physical properties are improved by blending zinc white in a kneading step of blending sulfur and the compound represented by the general formula (I) to prevent the polymer chain of the rubber component from being broken. Although it is characterized, an anti-aging agent that is usually used for the purpose of anti-aging derived from other factors can be blended, and the amine-based anti-aging agent is added in an amount of 0. 1 to 3 parts by weight can be blended, 0.5 to 3 parts by weight is preferable, and 1 to 2 parts by weight is particularly preferable. If it is 0.1 parts by weight or less, the effect of preventing aging is insufficient, and if it exceeds 3 parts by weight, bloom occurs, the appearance is deteriorated, and stability over time is lacking.

  Furthermore, sulfur can be mix | blended in the range of 1-10 weight part with respect to 100 weight part of rubber components, the range of 3-7 weight part is preferable, and the range of 4-6 weight part is more preferable.

  The rubber composition of the present invention can be produced by kneading the above components with, for example, a Banbury mixer, a kneader or the like, and can be suitably used as a sidewall portion of a run flat tire.

  Next, although an Example and a comparative example demonstrate this invention further in detail, this invention is not restrict | limited to these.

The blending contents shown in Table 1 below are divided into a kneading step before vulcanization and a step of blending the compound represented by sulfur and the general formula (I), and each component is blended in a Banbury mixer. By kneading, various rubber compositions, Examples 1 to 8 and Comparative Examples 1 to 3 were formulated.
<Production example of modified polybutadiene rubber>
To about 900 mL pressure-resistant glass container that has been dried and purged with nitrogen, 283 g of cyclohexane, 50 g of 1,3-butadiene, 0.0057 mmol of 2,2-di (2-tetrahydrofuryl) propane, and 0.513 mmol of hexamethyleneimine were added, Further, 0.57 mmol of n-butyllithium (BuLi) was added, and then polymerization was performed in a hot water bath at 50 ° C. equipped with a stirrer for 4.5 hours. The polymerization conversion rate at this time was almost 100%. Next, 0.100 mmol of tin tetrachloride as a modifying agent (coupling agent) was quickly added to this polymerization reaction system, and the mixture was further stirred at 50 ° C. for 30 minutes to carry out a modification reaction. Thereafter, 0.5 mL of a 2-propanol solution (BHT concentration: 5% by mass) of 2,6-di-t-butyl-p-cresol (BHT) was added to the polymerization reaction system to stop the reaction. The modified polybutadiene rubber (HMI-BR) was obtained by drying according to the method. The obtained HMI-BR had a vinyl bond content of the butadiene portion of 14%, a glass transition temperature (Tg) of -95 ° C, and a coupling efficiency of 65%.

[Aged physical properties] A vulcanized rubber sheet having a thickness of 2 mm obtained by press-pressing the rubber composition at 150 ° C. for 20 minutes was punched into a No. 3 dumbbell-shaped test piece, and JIS K 6301- A measurement test was conducted at 25 ° C. in accordance with 1995, and the elongation at break (EB) before aging was defined as the original EB, and the elongation at break after 24 hours at 100 ° C. was measured. / Evaluated as a percentage of the original EB. A larger value indicates better aging properties. The original stress at break (TB) was expressed as an index with Comparative Example 1 as 100.
[Run-flat durability] A run-flat tire using the above rubber composition as a sidewall portion was made as an experiment. Each prototype tire (tyre size 255 / 55R18) is assembled with a rim at normal pressure, filled with an internal pressure of 230 kPa, and allowed to stand at room temperature of 38 ° C. for 24 hours. Then, the valve core is removed and the internal pressure is set to atmospheric pressure. The drum running test was performed under the conditions of 19 kN (530 kgf), speed of 80 km / h, and room temperature of 38 ° C. The travel distance at the time of the failure at this time was the run flat drum travel distance, and was represented by an index with the numerical value of Comparative Example 1 being 100. The higher the value, the better the run flat durability.

* 1: NR: Natural rubber * 2: BR: Butadiene rubber * 3: Modified butadiene rubber * 4: Carbon black * 5: Process oil * 6: Anti-aging agent 6C: N-phenyl-N′-1,3-dimethyl Butyl-p-phenylenediamine (manufactured by Ouchi Shinsei Chemical Co., Ltd., trade name: Noxeller 6C)
* 7: Vulcanization accelerator DZ: N, N-dicyclohexyl-2-benzothiazylsulfenamide (Ouchi Shinsei Chemical Co., Ltd., trade name: Noxeller DZ)
* 8: Vulcanization accelerator TOT: Tetrakis (2-ethylhexyl) thiuram disulfide (Ouchi Shinsei Chemical Co., Ltd., trade name: Noxeller TOT)
* 9: Vulcanization accelerator a: Bis (2-benzothiazyl) disulfide represented by general formula (I)

  Comparative Examples 1 to 3, in which zinc white was blended in the kneading step before vulcanization and vulcanization accelerator a was used, were generally inferior in aging properties and run-flat durability, and in particular due to an increase in the proportion of natural rubber in the rubber component. The decline is great. In comparison, Examples 1 to 4, which used zinc white when blended with the vulcanization accelerator a, improved both aging physical properties and run-flat durability, and the decrease was small when the natural rubber ratio increased. Further, in Examples 5 to 8 in which a modified diene rubber and a secondary anti-aging agent were used in combination, further improvement in stress at break, aging physical properties and run flat durability were observed.

  By using the present invention, a run flat tire excellent in aging physical properties and durability can be obtained.

Claims (4)

When kneading the compound represented by the following formula (I), 1-3 parts by weight of zinc white and bismaleimide, 2-mercaptobenzimidazole, or 100 parts by weight of the rubber component containing the modified diene rubber A method for producing a run-flat tire sidewall reinforcing rubber composition comprising blending an imidazole compound that is a zinc salt thereof .

[R ¹ and R ² in the above formula (I) are a hydrogen atom, a linear alkyl group having 1 to 4 carbon atoms or an alkoxy group, a branched alkyl group having 3 to 4 carbon atoms or an alkoxy group, and these are the same. It may or may not be. ] When knead | mixing the compound represented by following formula (I), 1-3 weight part zinc white and the metal salt of methacrylic acid or acrylic acid are mix | blended with respect to 100 weight part of rubber components. A method for producing a run-flat tire sidewall reinforcing rubber composition.

[R in the above formula (I) ¹ , R ² Is a hydrogen atom, a linear alkyl group or alkoxy group having 1 to 4 carbon atoms, a branched alkyl group or alkoxy group having 3 to 4 carbon atoms, and these may be the same or different. ] The kneading method comprises a plurality of stages, a step of kneading a rubber component (A) containing natural rubber in an amount of 30% by weight or more with a filler, and a rubber composition obtained by the above step with sulfur and formula (I And kneading the compound represented by formula (I) with 1 to 3 parts by weight of zinc white with respect to 100 parts by weight of the rubber component. The method for producing a run-flat tire sidewall reinforcing rubber composition according to claim 1 or 2 , wherein The method for producing a run-flat tire sidewall reinforcing rubber composition according to any one of claims 1 to 3, further comprising 60% by weight or more of natural rubber.